如何使用PerlMagick提取EXIF数据？

Question

I'm currently using Perl Magick http://www.imagemagick.org/script/perl-magick.php , the perl interface to Image Magick http://www.imagemagick.org , to process & convert photos that our site users upload. I'd like to be able to also capture some of the EXIF data attached to these images and I have been able to figure out how to do this using the command line interface to Image Magick with the following command:

/usr/bin/identify -format "%[EXIF:*]" image.jpg

Which returns the following EXIF information for a particular photo:

exif:ApertureValue=29/8
exif:ColorSpace=1
exif:CompressedBitsPerPixel=3/1
exif:CustomRendered=0
exif:DateTime=2002:10:08 19:49:52
exif:DateTimeDigitized=2002:09:29 14:03:55
exif:DateTimeOriginal=2002:09:29 14:03:55
exif:DigitalZoomRatio=1/1
exif:ExifImageLength=307
exif:ExifImageWidth=410
exif:ExifOffset=192
exif:ExifVersion=48, 50, 50, 48
exif:ExposureBiasValue=0/1
exif:ExposureMode=0
exif:ExposureTime=1/1000
exif:Flash=24
exif:FlashPixVersion=48, 49, 48, 48
exif:FNumber=7/2
exif:FocalLength=227/32
exif:FocalPlaneResolutionUnit=2
exif:FocalPlaneXResolution=235741/32
exif:FocalPlaneYResolution=286622/39
exif:Make=Canon
exif:MaxApertureValue=12742/4289
exif:MeteringMode=5
exif:Model=Canon PowerShot S30
exif:ResolutionUnit=2
exif:SceneCaptureType=0
exif:SensingMethod=2
exif:ShutterSpeedValue=319/32
exif:Software=Adobe Photoshop 7.0
exif:WhiteBalance=0
exif:XResolution=180/1
exif:YResolution=180/1

I've tried about 100 ways to get this same result from Perl Magick but can't figure out how pass the same parameters I'm using on the command line to make it work properly. Here are a couple of variations I've tried none of which seems to have worked:

use Image::Magick;
my $image = Image::Magick->new;
my $exif = $image->Identify('image.jpg');
print $exif;

$image->Read('image.jpg');
$exif = $image->Get('format "%[EXIF:*]"');
print $exif;

I know there are other ways to extract EXIF data from an image file in perl but since we already have the Perl Magick module loaded I don't want to waste any more memory by having to load an additional module. I'm hoping someone out there already has this working on their site and can share the solution. Thanks in advance for your help!

Answer 1

> cat im.pl
use Image::Magick;
my $image = Image::Magick->new();
$image->Read('/home/rjp/2009-02-18/DSC00343.JPG');
my $a = $image->Get('format', '%[EXIF:*]'); # two arguments
my @exif = split(/[\r\n]/, $a);
print join("\n", @exif);
> perl im.pl
exif:ColorSpace=1
exif:ComponentsConfiguration=...
exif:Compression=6
exif:CustomRendered=0
exif:DateTime=2009:02:13 16:18:15
exif:DateTimeDigitized=2009:02:13 16:18:15
...

That seems to work.

Version: ImageMagick 6.3.7 06/04/09 Q16 http://www.imagemagick.org

Answer 2

I strongly recommend you to use Phil Harvey's ExifTool . It's comprehensive and well documented. Also, it doesn't read the entire image into memory, and according to the documentation you can get the Exif information from the image just by passing it a file handle to an open image file. So it shouldn't waste a lot of memory.

Answer 3

Edit: @rjp showed how to access all of the information rather than individual tags. Here is how to put the data in a hash:

#!/usr/bin/perl

use strict;
use warnings;

use Image::Magick;

my $image = Image::Magick->new;
$image->read('test.jpg');

my %exif = map { s/\s+\z//; $_ }
           map { split /=/, $_  }
           split /exif:/, $image->Get('format', '%[EXIF:*]');

use Data::Dumper;
print Dumper \%exif;